[Yokomatsu Hirame] Kareshi Mochi de Namaiki na Imouto to Sex no Renshuu suru Houhou | How to Practice Sex with My Bratty Younger Sister Who Has a Boyfriend [MTL]

An anxious brother hears his sister return home late at night, only to discover she plans to use him as a practice partner for mastering mind‑blowing oral techniques. She drags him into a heated encounter, forcing his participation while his bewildered reaction underscores the taboo dynamic. The twist arrives when she later admits the scheme was a lie, hinting that a brother vanished from Japan, leaving the brother to question the reality of their illicit training.